The Power Stretch Beanie by Mountain Hardwear is the hat to wear when using a helmet, or rain hat. Designed to fit tight and snug on your head with its Polartec Power Stretch fabric that has four-way stretch with an inside that is brushed to draw moisture away from the skin.

This is a great hat that fits perfectly under my hard hat while working out in the woods. I have used it for work, walking around, running and sitting by a campfire. It does fit a little large, but keeps the warmth in.

I've purchased 4 of these. They don't wear out, I tend to lose them. They are great for any activity and I especially like it for motorcycling. For running and other sweaty activities they dry up very quickly.

I spend more time in the outdoors than most. Everyday in the line of work I'm in. To find a warm hat that I like is usually hard to do. I like to use layers and it is no different for my head. I bought the power stretch gloves and liked them so much I decided to try the hat. If you have a big head this is the one for you. Nice and stretchy. A must have.

Good hat, works well as a helmet liner, it fits with the 2010/2011 version of the Black Diamond Half Dome helmet. I just wish a women's version was offered, that might improve the fit (for me at least). Overall good hat!

I had one of these for a couple of years and wore it for everything - snowboarding, skiing, hiking, running, and riding my Harley. I lost it this year when skiing and couldn't find another one anywhere. I ordered from this site but got the wrong hat. More research and I figured out it was this one. The ordering, return, and new order went so smooth. I purchased two this time! I wore my hat running this morning and then on the motorcycle ride to work!

I wore this hat for the first time a few days ago and I have to say that I am impressed. For the few runs that I have been on, the weather has been between 26 and 32 degress. My head was always warm even though I don't have complete coverage over the bottom of my ears. Overall, I would highly recommend this product.